1. Field of the Invention
The present invention relates to a tire for a motorcycle.
2. Description of the Related Art
An improvement of a highway network has advanced and a vehicle is caused to run at a high speed for a long time. A performance of the vehicle has been enhanced remarkably. In a tire to be used in the vehicle, a further enhancement in a critical performance has been demanded.
As a tire for a motorcycle, a radial tire is used. The tire has a carcass including a carcass ply. The carcass ply is turned up around a bead. The bead includes a core and an apex positioned on an outside in a radial direction of the core. The core includes a plurality of non-extensible wires. The apex is formed by vulcanizing a filler rubber. The apex is a crosslinked rubber. The crosslinked rubber has a hardness of 70 or more. The apex contributes to a stiffness of the tire.
A tire is formed by pressurizing and heating a green tire. A method of forming the green tire is as follows. First of all, a ring-shaped bead wire is formed by using the non-extensible wires and a topping rubber. Next, the filler rubber is combined with the bead wire so that a bead ring is formed. In the bead ring, the filler rubber is expanded like a flange outward in a radial direction of the bead wire. Next, a pair of bead rings are fitted in a carcass ply processed cylindrically. The bead rings are disposed in the vicinity of both ends of the carcass ply, respectively. Then, the both ends of the carcass ply are turned up so that the bead ring is enveloped in the carcass ply. Members such as a belt ply, a sidewall rubber and a tread rubber are further combined to form the green tire.
A pneumatic radial tire capable of contributing to a production efficiency has been disclosed in Japanese Laid-Open Patent Publication No. 2000-351306. In the tire, a sidewall includes a bead filler rubber disposed on an outside in an axial direction of a turned-up portion of a carcass ply, an abrasion rubber disposed on an outside in the axial direction of the bead filler rubber, and a sidewall rubber disposed on an outside in the axial direction of the abrasion rubber.
As described above, the manufacture of the tire having the bead constituted by the apex and the core includes the step of forming a bead ring by combining a filler rubber with a bead wire and then enveloping the bead ring in a carcass ply. In the step, the bead ring is laid down in such a manner that a side surface of the bead ring which is positioned on a side of an equator plane of the tire can come in contact with a surface of the carcass ply. The filler rubber expanded like a flange outward in the radial direction of the bead wire is rotated toward the equator plane side at approximately 90 degrees around the bead wire. In the formation of the green tire, a shape of the bead ring is changed. In the manufacture of the tire which includes the step, the step is to be controlled carefully in order to stably form the apex, the core and the carcass ply in proper positions of the tire. A great time and labor is required for manufacturing the tire. In the manufacture of the tire which includes the step, it is hard to further enhance the production efficiency.
In the tire described in the publication, the bead filler rubber is disposed on the outside in the axial direction of the turned-up portion of the carcass ply. In the tire, three types of rubbers including the bead filler rubber are disposed in the sidewall. In the tire, a reduction in a weight thereof is not considered.
It is an object of the present invention to provide a tire for a motorcycle which has an excellent productivity and a weight reduced.